What is already known
Compared to healthy babies born at term, preterm infants that weigh less than 1.5 kg at birth have altered gut microbiotas with lower diversity and more harmful bacteria, which can lead to serious conditions. While a mother’s milk is known to reduce these risks, very-low-birth-weight infants are often fed through tubes or using pasteurized donor milk. However, how these factors influence the microbiota of these infants remains unclear.
What this research adds
Researchers analyzed the microbiota in the milk of 94 mothers and in the gut of their very-low-birth-weight infants. They found that 30 to 40% of bacterial species in the infants’ guts are shared with their mother’s milk. Infants who were mainly fed mother’s milk were more likely to share bacteria with their mothers compared to those receiving mixed feeds that included pasteurized donor human milk. Antibiotic use disrupted the natural transfer of bacteria from a mother to her infant.
Conclusions
The findings confirm that mother’s milk can deliver beneficial bacteria to very-low-birth-weight infants, with feeding practices and antibiotic use influencing this microbial exchange.
Compared to healthy babies born at term, preterm infants that weigh less than 1.5 kg at birth have altered gut microbiotas with lower diversity and more harmful bacteria, which can lead to serious conditions. New research confirms that mother’s milk can deliver beneficial bacteria to very-low-birth-weight infants, with feeding practices and antibiotic use influencing this microbial exchange.
The findings, published in Cell Reports Medicine, may inform better feeding strategies for very-low-birth-weight infants.
These babies are often fed through tubes or using pasteurized donor milk, which can disrupt the transfer of beneficial microbes from milk to the infant gut. However, how these factors influence the microbiota of very-low-birth-weight infants remains unclear.
To address this question, Sara Shama at the University of Toronto in Canada and her colleagues analyzed the microbiota in the milk of 94 mothers and in the gut of their very-low-birth-weight infants.
Bacterial transfer
Most infants were given antibiotics for about six days after birth, and more than half of the mothers received antibiotics either in the two weeks prior to giving birth or shortly after giving birth. Nearly 70% of the infants were fed mainly mother’s milk, and about 30% were given mixed feeding supplemented with pasteurized donor human milk, which no longer contains live bacterial cells due to the pasteurization process. Half of the infants received human milk-based fortifiers — additives used to increase the nutritional content of milk.
The researchers looked for associations between bacteria in mother’s milk and their concentrations in the infants’ stools. Bacteria present in milk were typically found also in the infant’s gut, except for Corynebacterium, Clostridium sensu stricto, Haemophilus, and Bifidobacterium.
Infants who were mainly fed mother’s milk showed stronger associations, and breastfeeding increased the likelihood of observing Veillonella and Haemophilus in both milk and stool. “We identified direct breastfeeding as a key modifier of microbial sharing between mother’s milk and the infant gut,” the researchers say.
Antibiotic use
Babies whose feeding was supplemented with fortifiers showed microbial patterns that resembled those observed in infants fed with mother’s milk. However, human milk-based fortifiers were linked to microbial patterns similar to mixed feeding with pasteurized donor human milk. These results suggest that different fortifiers can modify the bacterial transfer between milk and the infant’s gut, the researchers say.
The team also examined the impact of antibiotic use on the transfer of bacteria between a mother an her infant. Antibiotic use, in both mothers and infants, disrupted the natural bacterial transfer, weakening the association between bacterial intake from milk and microbial diversity in the infant’s gut.
These findings, the authors say, “highlight that discussions around antibiotic stewardship are needed for both mothers and their preterm infants, since exposure in either group may carry potential short- and long-term consequences for the developing infant.”
